cpython-internals

Why Mutable Default Arguments Are Structurally Dangerous in PythonMutable default arguments are one of the most persistent sources of surprise in Python. A function appears to start with a clean default value, yet state leaks across calls.The behavior looks like a bug. Each invocation feels independent. The function body does not obviously store global state.Despite this, lists grow unexpectedly..

Why Shallow and Deep Copy Fail in Real Python CodeCopying objects in Python feels like a solved problem. A shallow copy duplicates the container. A deep copy duplicates everything. The intent seems clear.In practice, copied objects still leak state. Mutations propagate unexpectedly. Performance degrades. Subtle bugs survive testing and surface later in production.This creates a false sense of sa..

Why Python Garbage Collection Looks Like It Is Not RunningMany Python developers assume that a garbage collector is constantly scanning memory and reclaiming unused objects. When memory usage stays flat or keeps growing, it feels like the collector is stalled or broken.This impression becomes stronger when manual calls to the garbage collector appear to do nothing. Objects remain alive. Memory d..